Surface-modifying tools

ABSTRACT

In a method for removing metal from the surface of a workpiece by continuously rubbing the surface with a tool in a friction-inducing manner and in the presence of a friction-enhancing agent (an anti-lubricant) and in which a thin layer of the friction-enhancer must be available at the tool surface, there is provided a tool which carries the friction-enhancing agent in the form of a composition of an abrasive and a rubbery solid siloxane reaction product admixed with a liquid, mobile, anti-lubricant siloxane stably dispersed therewithin, and the use of the tool to excoriate and condition the surface by removing therefrom the oxide film thereon and leaving its place a siloxane film, and a conditioned metal surface having siloxane molecules each individually bonded directly to the metal over a relatively large area of the surface to provide a relatively uniform siloxane layer.

This invention is concerned with surface-modifying tools. Morespecifically, it relates to abrasive tools for modifying the surface ofa metal part so as to shape that part or to condition that surface, andit concerns the use of these tools to do these things. It also relatesto metal parts thus shaped or conditioned--and in addition it pertainsto conditioned-surface metal parts prepared in related but slightlydifferent ways.

In the Specification of our International Patent Application WO93/24,272 (=GB No: 2,267,242A: P1285) there is described and claimed amethod of removing metal from the surface of a metal workpiece bycontinuously rubbing that surface with a tool in a friction-inducingmanner and in the presence of a friction-enhancing agent (ananti-lubricant) in a quantity and in a form such that actual frictionenhancement occurs. It is explained how, in the case of surface-shapingrubbing tools such as grinding wheels, some extra workpiece materialthat is in frictional contact with the tool is sheared from the surfaceas a result of the increase in kinematic coupling as the frictionbetween tool and workpiece rises, and hence the abrasive tool efficiencyis improved.

Operating experience has shown there are many uses for theabove-mentioned friction-enhanced shaping of metals, and in particularfor those varieties of shaping methods using abrasive media.Furthermore, experience has shown that it is essential that anappropriately thin layer of the friction-enhancer always be available atthe surface of the tool, where it makes contact with the workpiece, andis actually carried between the rubbing surfaces as the tool rubsagainst the workpiece. In the above-mentioned PCT Specification severalways of applying the preferred friction-enhancers, which are siloxanes,are described. In particular, one commercially-attractive method isdescribed involving impregnating and reacting a layer of siloxane ontothe vitreous structure within a porous grinding wheel. This system worksparticularly well when sufficient new wheel surface is created (dueprincipally to re-dressing, or to a lesser extent, to wear) to allowfresh siloxane to reach the surface, as is the case with frequently- orcontinuously-dressed wheels. However, in some cases the wheel surfacelasts longer in the presence of a siloxane, and as a consequence undersome operating conditions the supply of siloxane to the surface canafter some time become minimal, and in extreme cases inadequate for thepurpose of maintaining the sought-after improvement of cutting for thelife of the wheel.

Moreover, experience has shown that after prolonged operation under someconditions the siloxane impregnated into the wheel suffers slowdegradation near the contact zone around the rim of the wheel. It isthought this is due to the high temperatures near the contact zone, aswell perhaps as to the long term exposure of the wheel to the fluidsused as the coolant.

The present invention in one of its several related aspects suggests asolution to these two problems; it proposes a novel type offriction-enhancing-agent-carrying abrasive rubbing tool (and its use ina method like that of the aforementioned Specification) in which thefriction-enhancing agent is carried by the tool in the form of acomposition of an abrasive and a rubbery solid siloxane reaction productadmixed with a more liquid, mobile siloxane (that itself has thenecessary anti-lubricant, friction-enhancing properties)immobilised--stably dispersed--within the reaction product. Forinstance, the present invention proposes that the tool be impregnatedwith a siloxane reaction-product curable fluid that contains withinitself a siloxane with friction-enhancing anti-lubricant properties,this fluid being cured within the tool into a rubber-like material thatadheres to the structure of the tool and that slowly and evenly releasesthe anti-lubricant siloxane therein as the tool is used. Ideally, thisreaction-product material is evenly distributed throughout the poroustool structure, and in fact forms a secondary structure therein. Thefree anti-lubricant siloxane contained therein is able slowly to escapeunder the mechanical forces of the tool spinning (or reciprocating toand fro, or whatever is appropriate). Indeed, in the case of grindingwheels or coated abrasive discs the free friction-enhancing siloxane isprobably released some distance away from the contact zone, and thusaway from where it is thought it might be damaged by high temperature orcoolant fluids, and migrates to the rubbing surface where it is carriedinto the contact zone to maintain a fresh supply of new, undamaged,friction-enhancing siloxane.

In another related aspect, however, the invention concerns the use oftools (rather like those just described) not to abrade the metal part'ssurface in some significant manner (which would result in the toolactually cutting down into the underlying metal, so shaping the metalpart) but instead merely to excoriate the metal part--to remove byrubbing abrasion a very thin surface layer or skin, and specifically toremove little more than the oxide film inevitably formed on the surface,leaving the surface clean, bare metal. Such excoriating, rather thanshaping, tools are the result of the work leading to the shaping-toolinvention; while doing this it was discovered that during relativelylight abrasion where the metal being shaped was protected from exposureto further oxygen, and was allowed to remain covered with a layer orcoating of siloxane, the metal was imbued with certain surprisingproperties.

Firstly, it was found that the coated metal appeared to havesignificantly-improved anti-corrosion properties--and, specifically,resisted atmospheric corrosion (reaction with atmospheric oxygen). Iron,for example, either didn't go rusty, or showed only a minimal rustingeven after a very long time.

Secondly, it was found that the coated metal seemed to provide a muchbetter base for a subsequent layer/coating of adhesive or paint.Standard tests showed a very considerable increase in the tenacity of anadhesive coating applied to a siloxane-coated steel plate as comparedwith one applied to an uncoated plate.

This lead to a second novel type of tool, and a second major aspect ofthe invention, namely a mildly--abrasive rubbing tool (and its use in amethod of providing a metal part with a specially-conditioned surface)in which a siloxane, chosen for its ability to imbue the surface withsome desired special property, is carried by the tool in the form of acomposition of a fine abrasive and a rubbery-solid siloxane reactionproduct admixed with a more liquid, mobile siloxane (that itself has theappropriate property-imparting nature) immobilised--stablydispersed--within the reaction product. The chosen siloxane may, forinstance, be either a friction-enhancing agent or a lubricating agent,it may be hydrophilic or hydrophobic, and it may show enhancedcompatibility or reactivity with certain types of chemicals (and thechemical might be some biological material so that the conditionedsurface displayed some biochemical activity).

Further work carried out with this type of excoriating tool revealed anumber of interesting features. For example, the criteria forconditioning being somewhat different to those involved in shaping, itwas not actually necessary to use a siloxane in the form of a rubberysiloxane reaction product composition; instead, it was possible toprepare very satisfactory conditioned metal surfaces by carrying out theexcoriation with practically any mild abrasive and in the presence ofany appropriate siloxane.

Thus, in yet another related aspect the invention concerns a method ofconditioning a metal part (so that it carries bonded to its surface asiloxane layer) by first excoriating the metal surface in the presenceof a siloxane and under oxygen-excluding conditions, to clean off theoxide film therefrom, and then further rubbing it in the presence of asiloxane to form on the clean surface the desired layer of individualsiloxane molecules bonded directly thereto.

And the thus-formed conditioned surfaces are in fact both novel andinventive--and useful--in themselves, and accordingly in a still furtherrelated aspect the invention pertains to a metal part with a conditionedmetal surface having siloxane molecules each individually bondeddirectly to the metal over a relatively large area of the surface toprovide a relatively uniform siloxane layer.

These various aspects of the invention will now be discussed in moredetail.

The tools

In a first aspect the invention provides an abrading tool whichcomprises:

a substrate on the surface of which, and optionally in the body ofwhich, is carried an abrasive composition itself comprising

an abrasive admixed with

a rubbery composition

which is the reaction product of a reactive polyfunctional siloxaneco-polymerized with itself or with one or more other reactivepolyfunctional siloxane to form a rubbery-solid material, this reactionproduct being admixed with a liquid, mobile siloxane which is stablydispersed therewithin.

The tools of the invention may notionally be divided into those intendedfor shaping an object--for being applied to the object's surface to wearaway significant quantities of the object material--and those intendedfor excoriation (and conditioning)--for skimming off a thin skin (thevery surface layers) of the object to reveal the clean materialunderneath (where the object is a metal such as iron or an alloy thereoflike steel the surface stripped off is usually merely the oxide layer,revealing clean, bare, metal). This division will commonly be on thebasis of the hardness and stiffness of the tool substrate, of thecoarseness of the abrasive, and of the anti-lubricant or other nature ofthe mobile siloxane; hard, stiff, coarse tools will abrade awaysignificant amounts, and so will shape, whereas soft, flexible, finetools (regardless of the siloxane) will merely excoriate. And naturallythere will be some overlap: some tools may be usable for either purpose,it depending on quite how, and for how long, they are utilised.

Types of tool and metal-removal

i) Shaping tools

The invention's shaping tools can be applied to almost any kind ofmaterial-removing and--shaping process provided that there be used atechnique involving rubbing friction to be enhanced by the presence ofthe anti-lubricant siloxane, and so there may be used almost any kind oftool on almost any kind of workpiece. Thus, the tool can be applied toconventional machining (as done using a lathe, or a milling machine, ora saw, provided the tool itself rubs), and--and especially--to any ofthe various forms of abrading processes.

All the above-mentioned processes used in the shaping of a metalworkpiece depend on the removal of many small slivers from its surfaceon each successive rubbing contact (the rubbing friction causes weldingbetween the tool and the surface, and the material under the rubbingcontacts is then sheared off by the continuing tool motion). The size ofeach sliver is small, estimated to be of the order of 0.001 m³ for softmaterials and less than this for hard materials. In the case of amulti-contact tool system like a wire brush (perhaps with polishedterminating balls anchored to the end of each wire), or "flex hone" (awire brush with abrasive balls anchored to the ends of the wires) or agrinding wheel, many thousands of contacts can be made and sliversremoved within a second to give a satisfactory metal removal rate.

The tool substrate can be of many different kinds, ranging from theextremely hard material of a conventional grinding wheel (for shaping)down to the softest of tissue papers (for excoriating). Varieties oftool are now discussed to illustrate this.

A grinding wheel is an abrasive tool, along with honing stones, lappingstones and pastes, electroplated-diamond--and--cubic-boron nitridereamers, linishing belts, discs, de-burring mediums, and many others.All the abrasive tools depend on rubbing to create the essentialtool/workpiece interface motion between randomly orientated small grainsof hard material. This brings the individual cutting tools (grains) intocontact with the workpiece surface to give them the opportunity to cut.Only those cutters with favourably positioned cutting edges and surfaceswill actually cut (and in most abrasive systems this is less than 50%);those with unfavourably-positioned cutting edges and surfaces simplycause friction heat due to ploughing (plastic deformation) and rubbing.The tool of the invention will improve the efficiency of all theabove-mentioned shaping methods because it uses the otherwise-wastedheat energy to cause the microwelding that results in additionalmaterial removal.

ii) Excoriating, conditioning tools

In its excoriating, conditioning guise the tool of the invention may beof the type of many of the conventional abrading, de-burring andfinishing tools utilised in industry save for its employment of fine, ormild abrasives, such as those tools using abrasive-loaded nylonfilaments, non-woven abrasive materials, coated abrasive belts, flapwheels, and cloth buffs.

One particularly interesting variety of excoriating, conditioning toolis that which is little more than a sheet of paper coated or impregnatedwith the abrasive/rubbery-siloxane composition; this type can range fromflimsy absorbent papers (almost like tissue paper) to rather stiffer,more substantial papers (like those referred to as "sandpaper" or"glasspaper").

In the case of flexible tools based upon a fabric or paper substrate therubbery siloxane composition can be used to bond the abrasive onto, andinto, the substrate. Indeed, if treated with a composition containing afine abrasive--or, and preferably, if dusted with abrasive and thengiven a coating of the rubbery material to form the desired abrasivecomposition in situ on the surface--a simple sheet of paper can become auseful excoriation tool for surface conditioning, similar to finesandpaper or emery paper. If the substrate is absorbent and the siloxanecomposition is applied thereto in its raw, unreacted-component form sothat it soaks into the material and there cures to the desired rubberyconsistency, this can be used to bind the abrasive securely to (andinto) the surface. Moreover, applying the siloxane composition in thatraw, liquid form to a porous substrate such as paper or cloth permitsthe making use of the adhesive nature of the composition to effect thebonding of the substrate to a firmer support as the composition cures toits desired rubbery form.

In the case where the absorbent material substrate is a sheet of paperthe abrasive tends to concentrate at the surface to which it is applied,while some uncured fluid soaks into and through the paper, so that thereis formed a "double-sided" paper the first side of which carriesabrasive, and so has a relatively substantial abrasive action, and thesecond of which has only a very mild abrasive, orpolishing/conditioning, effect due mainly to the paper fibres. Thus, byfirst rubbing with the coated abrasive side and then turning the paperover and just using the impregnated surface, an exceptionally fineconditioned surface finish can be obtained on most metals.

Tools made from treated paper can use either a relatively light qualitypaper or--for a superior effect--a purposely absorbent paper--a Kraftpaper, or one of those types such as those marketed under the trade nameABSORBEX (manufactured by Laminating Papers Ltd. Kanavaranta 1, PO Box309, Helsinki, Finland). These papers are designed to absorbimpregnants, and will swell and hold considerable amounts of cured oruncured composition. Moreover, as the paper swells so the pores at itssurface open and allow some of the (fine) abrasive to be drawn into thestructure (though even so most--and especially the coarsercomponents--remains close to or at the surface). The effectiveness ofthis combination as an abrasive tool is ultimately determined by thestiffness of the backing provided. As described hereinafter withreference to the Examples, one of the abrasives used in preliminarytests was white 320 grit fused alumina; this provided a good surfacepolishing action well suited to excoriating a mild steel surface.

Many commercially-available papers are in fact designed for laminating,and it is possible, by using many layers of a lightweight paper, tobuild a laminated construct of individually-impregnated layers thatforms an altogether heavier and more substantial structure, suited foruse in abrasive tools like sticks, wheels, rollers or even thickflexible belts (and the rubbery siloxane composition also serves to bondthe layers together). Some fibrous or thin metal mechanical backing canadditionally be incorporated in such a structure.

Another interesting and useful material for impregnating with a rubberysiloxane composition and use in the invention is cloth, particularly oneof the many varieties of non-woven cloth. A typicalcommercially-available instance of this sort of cloth comprises a blendof 80% polypropylene/20% cotton--for example, those sold as grade HWC 35or 50 by Bonded Fibre Fabric Ltd. of Bath Road, Bridgwater, Somerset,UK. The surface of many of these materials is indented, and, while thevery fine components of the abrasive in the unreacted liquid compositionsoak down into the material, the coarser components accumulate in andfill the indentations. Thus, a small amount of relatively coarseabrasive can be added to and mixed with a larger amount of fineabrasive, the former's particle size being chosen so the depth of theindentations in the treated material surface is able to carry the coarseabrasive without it protruding awkwardly above the fine. The blend canbe selected according to function, but the combination makes a moreaggressive abrasive when using a hard backing (if a soft backing is usedthe larger abrasive has little effect). Thus, by varying the backingstiffness or rigidity it becomes possible to adjust the effectiveabrasive nature of the tool, this feature hitherto only being possibleby changing the grain size (which normally means changing the toolitself).

One other, and quite different, possibility for the tool is to make theentire tool out of the rubbery composition--in other words, thesubstrate is the rubbery siloxane composition, fashioned into arubber-like body that itself actually constitutes a tool. For example, amixture containing either one or more grades of abrasive can be mouldedinto a shape or into a recess in a tool post or holder.

iii) Making the tools

In the above discussion of the tools themselves there has been made somereferences to how the abrasive rubbery composition is actually appliedto the substrate. For the most part, the composition can be prepared asa liquid mixture of all the ingredients--that is, the abrasive, themobile siloxane, and the reactive siloxane components of the desiredrubbery product--and then applied to the substrate as it is curing.Sometimes, however, it may be convenient to add the abrasive componentin situ rather than beforehand. For example, when making a shapinggrinding-wheel tool it may actually be necessary first to load the wheelwith the fine abrasive--vibrating it in--and then to soak in the liquidsiloxane composition, which cures in place to give the desired abrasivecomposition (and a similar technique can be used when the substrate is aflexible cloth or paper).

Moreover, where the rubbery composition is one which is desirably curedwith a catalyst, then, to extend the working life of the variouscomponents, it may be preferred not to mix the catalyst with thecomponents and then apply the mixture to the substrate but instead tosoak the catalyst onto or into the substrate and then apply theremainder of the composition thereto.

The abrasive composition

a) The abrasive

Whether for shaping or for excoriating/conditioning, the tools of theinvention have on (or in) their substrate an abrasive composition itselfcomprising an abrasive admixed with a rubbery siloxane composition. Theabrasive may be any of those materials used, or suggested for use, forthat purpose, and may range from extremely coarse (for shaping) toextremely fine (excoriating/conditioning) materials. Typical suchmaterials are alumina, silicon carbide, cubic boron nitride (CBN), anddiamond, each available in grit sizes from coarse--size 20 (1,000micrometer)--to fine--size 1,200 (4 micrometer). Some comments about theabrasive and its use and effect now follow.

The rubber-like solid forms a secondary structure within or at thesurface of the primary structure provided by the tool substrate; thissecondary structure binds in and retains the added abrasive--which willmost usually be fairly fine, typically a 320 grit (with particles sizedat 30 microns and less)--but which can be quite coarse, typically agrade 120 or less. Where the tool itself is an abrasive structure, suchas a grinding wheel or disc, the rubbery composition's abrasive is thusa secondary abrasive (and is occasionally referred to as suchhereinafter for convenience). Such a secondary abrasive is addeddeliberately, but may also spontaneously appear as the tool actuallywears down the surface of the workpiece, being a mixture of microscopicparticles derived both from the workpiece surface and from the toolitself. A deliberately-added secondary abrasive migrates into therubbing zone as the tool is used--thus, as a grinding wheel spins--tocreate more rubbing contacts. This is particularly advantageous whenmachining hard materials that do not plasticly deform when in rubbingcontact with the tool, for the fine secondary abrasive will penetratethe rubbing interface with the friction-enhancer, and will then createmany extra microscopic rubbing sites when trapped and packed togetherbetween the hard main abrasive and the hard workpiece surface. Thefriction of each of these sites will be individually enhanced by thefriction-enhancer, and this rapidly builds up to give the requiredkinematic coupling needed to shear off hard surface material. It isimportant to note that the observed useful increase in metal removal isachieved only when testing against hard steel; no significant increaseis observed when abrading a plasticly-deformable mild steel, for therethe basic tool's effect is already as great as can be expected.

And perhaps surprisingly, the use according to the invention of one ofthe defined rubbery solid siloxane compositions can be of benefit evenwhen applied to tools with what might be thought of as non-porousstructures (a sanding disk, for example); by coating the surface of thetool so the stored siloxanes and abrasive are retained within theroughness of the surface.

Adding the abrasive might seem unnecessary when the tool is a shapingtool which is already highly abrasive, as is the case with a grindingwheel or disc, rather than an excoriating, conditioning tool, but infact that is not the case. The abrasive has an unsuspected benefit; itseems that the rubbery compositions used in the invention may, underunfavourable conditions, actually act as lubricants when trapped betweenlarge low pressure rubbing areas because their large molecules canmaintain tool/workpiece interface separation under light mechanicalcompression. This is detrimental to the shaping method of the invention,which seeks to promote friction between the surfaces, and it is at leastpartially to combat this possibility that the abrasive is added to thecomposition, for the particles of the former tend to bridge theseparation gap created by the large molecule reaction products in thelatter, and thus prevent lubrication occurring (and for this to be mosteffective it is desirable that the rubbery composition be chemicallyweak, and thus relatively easily degraded to release the abrasiveparticles).

As intimated above it is thought that the added (secondary) abrasivemainly cuts not by conventional shearing, as an ordinary abrasive does,but instead by frictional shear. To explain this belief it is importantto distinguish between the behaviour of a fixed (primary) abrasive (ason a grinding wheel) and that of a "free" one (as is effectively thecase with the added, secondary, abrasive retained in a rubbery matrix).The attitude (orientation) of the immovable abrasive grains in a toollike a grinding wheel are fixed in relation to the work surface, andcannot change, and it is this rigidity that enables a grain, when one ofits cutting edges is favorably oriented, to shear/cut/chisel materialfrom the surface, like butter scraped up with a firmly-held knife. Bycontrast, a "free" grain will under the applied forces adjust itsorientation to take up positions of greatest stability, and these occurwhen flat slides against flat--when a flat grain surface slides againstthe flat workpiece surface--like the situation in which the knife isheld so loosely that it rotates in the hand, and merely wipes across thesurface. Hence, a secondary abrasive grain--a grain that is basicallyfree, albeit constrained or retained within the rubbery matrix--withmany flats will be most stable when it is trapped between the tool andworkpiece with a flat in contact with each--in other words, when it hasachieved the maximum possible contact area. This is not only the moststable condition but it is also the best rubbing condition. Thus, it isbelieved the free abrasive only acts as a rubbing abrasive and doeslittle or no conventional shear cutting. However, this rubbing is justwhat is wanted; when rubbing friction is increased, at some point thefrictional coupling will be so great that kinematic coupling occurs andshears surface material off. It is this that causes the improvement inmetal removal when utilising a secondary abrasive.

b) The rubbery siloxane composition

The rubbery composition used in the invention's tools is the reactionproduct of a reactive siloxane co-polymerized with itself or with one ormore other reactive siloxane to form a rubbery solid material.

This rubbery solid is preferably fairly soft--and may even be more likea gel than a true solid--so that: it can deform and release the storedmobile siloxane; it will slowly creep and break up under the prolongedinfluence of tool-operating forces to release the abrasive; and it isdragged into and so penetrates the tool/workpiece interface. Ensuringthat it is fully reacted gives it good long term stability and excellentshelf life. The less reacted and more gel-like materials--although thesetend to dry out over long periods of time, and so have a more limitedlife than the fully-cured rubbers, they are easier to use as carriers ofsome of the more reactive and sensitive mobile siloxanes (themethyl-hydrogen ones, for instance), and so may have definiteadvantages--will behave almost like a very thick viscous fluid with ahigh surface tension able to wet onto and stick to a surface but onlyslowly to flow under the operating forces of the tool. A gel-likerubbery material will, because of its high surface tension, resiststatic creep, but it may creep under certain dynamic conditions--suchas, for instance high "G" forces encountered in handling ortransportation. It will effectively retain the additional siloxanewithout serious risk of this leaching out, both before and after drying(though in the latter case its contained mobile siloxane can stillescape under the influence of the mechanical forces of the tool). Gelcompositions are best suited for application to the surface of a toolsubstrate; because of their immediate relatively high viscosity they arenot suited to being absorbed into the body of the substrate.

Compositions having the required properties are now described.

The rubbery compositions used in this invention contain the cross-linkedreaction product of a polyfunctional siloxane with either itself(perhaps with the assistance of a cross-linking agent such as a reactivesilane) or with at least one other, different, polyfunctional siloxane(so that the composition is made up of at least two different monomericunits each of which is itself a polyfunctional siloxane polymer; theproduct is thus a co-polymer). These siloxane materials arepolyfunctional in that each contains at least two, and preferably atleast three, functional groups (which may be the same or different) bywhich it can react with, and so attach itself to, the other to form aloose three-dimensional matrix capable of holding the relatively mobilesilicone therewithin. Moreover, they are siloxanes--that is, they arethemselves silicone polymers made up of many units derived from moietiesof the type ##STR1## wherein R¹ is an alkyl group, and R² is the same ora different alkyl group (the preferred alkyl group R¹ and R² is themethyl group); these siloxane starting materials are themselvesconveniently prepared by reacting corresponding compounds wherein someof the R groups are hydrogen with the donors of the required functionalgroups. The more useful starting siloxanes seem to be those ofrelatively limited reactivity, and those of relatively low molecularweight, and thus relatively short chain length (the number of the abovemoieties in each unit is conveniently, but not necessarily, from below10 to above 300.

As to the functional groups, these can, within reason, be almost any setof groups capable of reacting one with another to form the desiredpolymeric product. One suitable pair of such groups is amine anddicarboxylic anhydride, ##STR2## which react together, two amine to oneanhydride, to form amide linkages ##STR3## many of which will result inseveral molecules being cross-linked eventually to form a matrix havinga complex dimensional structure (this sort of reaction product isparticularly useful in forming gel-type compositions).

Depending upon the polyfunctionality of the monomers chosen, thereaction product may be a linear polymer and yet, by virtue of the shapeand 3D nature of the monomers, have a 2D or even 3D shape of its own, orit may be a 2D macromolecule, rather like a net, or a 3D macromoleculelike a sponge. Moreover, even where the product is mostly sheet--ornet-like, it may be interlinked so as to result in a loosethree-dimensional structure. The problem is that determining thephysical shape and structure of giant molecules such as these isextremely difficult, and at this time it is not easy to provide anyinformation thereon except educated guesswork.

As will be apparent, the possible polyfunctional siloxanes may have awide variety of forms, but are preferably polydimethyl siloxanes. Mostpreferably they are of relatively low molecular weight (and thus have arelatively short chain length). Typical actual materials are thefollowing:

Masil 28 This is a "hydrosilicone" supplied by Mazer (PPG) Chemicals. Itis believed to be a polydimethylsiloxane (with around 100-110dimethylsiloxane monomer units) typically containing four active acidanhydride groups. It has a molecular weight of about 8,000, and aviscosity of around 130 c/s, and is said to be disclosed in PPG U.S.Pat. No: 4,876,152.

DC 109 Supplied by Dow Corning, this is thought to be ahydroxy-terminated polydimethyl siloxane (estimated chain length600-650, molecular weight 47,000 and viscosity 4000 c/s).

DC 1107 Supplied by Dow Corning, this is a polymethylhydrogen siloxane(estimated chain length 30-35, molecular weight 2,600, viscosity 30c/s).

Rhodorsil Oil 21637 Another amino functional material fromRhone-Poulenc, believed to be a diamine polydimethylsiloxane (chainlength estimated at 160-180, molecular weight 13,500, viscosity 300 c/s;amine content 4,200 ppm).

Rhodorsil 48V50 to 1,000,000 A series of materials from Rhone-Poulenc.They are thought to be hydroxy-terminated polydimethylsiloxanes(estimated minimum chain length 50, molecular weight 3,800, viscosity 50c/s).

Silane A-1120 N(beta-aminoethyl)-gamma-amino-propyltrimethoxysilane. Adiamino-functional silane from OSi Specialities.

Silane Y-11343 This is an organofunctional silane crosslinker andadhesion promoter supplied by OSi Specialities, with a viscosity of70-100 cSt and a total amine content equivalent to 2.7-3.0 moles N/kg.

In one case the cross-linked rubber-like reaction product is formed byfirst mixing the reactants with the free siloxanes before a finalcatalyst is added. Immediately after applying the catalyst the mixtureis--should be formulated to be--a fairly low viscosity liquid of between200 c/s and 600 c/s; as such it can be applied to a surface wherenormally it will cure at room temperature trapping the free siloxanessecurely within its structure. The cure time varies from less than fourhours to as long as several days, depending on the formulation and theconditions.

The liquid siloxane compositions developed will, when catalysed, cure atroom temperature to the desired rubbery form with good adhesion ontomost dry, clean, degreased surfaces--in particular to the impervioussmooth surfaces of many plastics, vitreous materials, ceramics, metalsor the cured resins often used to secure the abrasive in coated abrasivesystems. When applied to permeable surfaces like paper or woven fabricor a non-woven cloth the liquid composition will absorb or soak into thematerial before curing, which causes non-woven cloth to swellnoticeably. When applied to an open porous body like a grinding wheel itwill soak in and penetrate deep into the porous tool, and bond to theinterior surfaces of the structure as it cures.

It is important to note that the cross-linking or "vulcanization" of thesiloxane reagents forming the uncured liquid composition can take placein the presence of the free siloxanes even after absorption of theliquid composition either into another material like paper or into theconfined spaces within the porous structure of a tool like a grindingwheel.

c) The immobilised mobile siloxane

The siloxanes useful in the abrasive compositions employed in the toolsof the invention may take a number of different forms, and may becategorised, as convenient, either by their purpose and effect or bytheir chemical type. From the point of view of purpose and effect achosen siloxane may, as stated above, be either a friction-enhancingagent or a lubricating agent, it may be hydrophilic or hydrophobic, andit may show enhanced compatibility or reactivity with certain types ofchemicals. It might even have a pre-defined bio-compatibility. From thepoint of view of their chemistry, however, the siloxanes found so far tobe useful in this invention are on the whole diorganyl siloxanes of theGeneral Formula

     --O--Si(R.sub.2)--!.sub.n

wherein n is from 3 to 20, and each R group, which may be the same ordifferent, is selectable from hydrogen and a vast range of organicmoieties, mostly hydrocarbyl and poly(oxyhydrocarbyl) (includingsubstituted versions thereof) groups with from 1 to 14 hydrocarbylunits. As is further explained hereinafter, the side, or pendant, groupsR are the generators of the siloxane's properties; these properties aredetermined both by the main body of the pendant group and by theparticular terminator substituent groups--methyl, hydroxy, thiol, amino,halogen, carboxy, epoxy or ethenyl or ethynyl, for instance. The shortersilicon chain siloxanes--and particularly those wherein n is 3--seem tobond to the underlying metal surface rather more easily and more denselythan do the longer chain materials, and this is particularly so forthose with the longer pendant chains R.

Moreover, while any particular siloxane will for the most part be usedon its own, there may be occasions when a blend, or mixture, of two ormore different siloxanes may be appropriate.

i) Friction-enhancing siloxanes

Those tools of the invention intended for shaping by the abrading awayof significant amounts of workpiece material rely on the use of afriction-enhancing anti-lubricant diorganyl siloxane.

The medium molecular weight siloxanes (wherein the hydrocarbyl etcgroups R are fairly long chain) are oils, and many of these oils have inthe past proved to be useful as lubricants. In clear contrast, thesiloxanes suitable in the present invention as anti-lubricants are lowmolecular weight, short-chain hydrocarbyl or hydrocarbyl/hydrogensiloxanes. Indeed, those siloxanes in which the hydrocarbyl groups areshort-chain alkyl groups--and specifically those wherein the alkylgroups are methyl groups--seem to be the best anti-lubricants.Accordingly, for use in the present invention there is very preferablyemployed, as the material promoting the friction enhancement (as theanti-lubricant), a siloxane of the dimethyl or hydrogenmethyl type.Particular silicones are discussed further hereinafter.

The siloxane friction enhancing agent may itself directly promotefriction enhancement, or it may do so indirectly, by giving rise underthe conditions of use to a material that does itself promote frictionenhancement--say, by breaking down chemically into a form that promotesfriction enhancement when subjected to the heating (chemical) or shearforces (mechanical) generated during their use. It is believed that thesiloxanes, or their break-down products, also act to remove any surfaceoxide (and possibly to stop such a layer re-forming, perhaps byscavenging free oxygen from the environs; this is thought to beparticularly so for the hydrogenmethyl siloxanes).

The anti-lubricant, friction-enhancing action of silicone oils,particularly the polydimethylsiloxanes, was first exploited to gall andjoin metals as described in the Specification of our InternationalPatent Application WO 91/19,589 (P1220). Their behavior asfriction-enhancing agents is more moderate under the ambient conditionsof the rubbing used in the shaping method of the invention, butnevertheless similar materials are suited for use therewith (although insome instances it is beneficial to blend them with other substances, tomatch operating needs). Preferred anti-lubricant siloxanes for use inthe present invention are liquids and of relatively low viscosity (about50 c/s or less, some as little as 10 c/s). The particularly-preferredmedium molecular weight polydimethylsiloxanes are of this sort,especially those materials commercially available from Dow Corning underthe Marks MS 200, and Dow Corning 344 and 345, all of which are fullydescribed in the relevant Data Sheets. The 344 and 345 materials,normally used in cosmetic preparations, are respectively blendspredominately of cyclic tetramers and pentamers of dimethylsiloxane.Other preferred silicones are mentioned below.

ii) Siloxanes suitable for conditioning

The siloxane need not be an anti-lubricant, friction-enhancer; it maywell be desirable, when conditioning a metal part's surface using anexcoriating tool rather than shaping it with an abrading tool, toprovide that surface with a layer having some other sort of effect(although in fact many of the preferred anti-lubricant siloxanes have,and can also be used for, one or more other conditioning effect). Forexample, there could specifically be afforded to the metal part'ssurface a lubricant effect (as opposed to an anti-lubricant one) orhydrophobic or hydrophilic properties. The conditioning characteristicsconferred on the surface are governed by the chemistry of the depositedsiloxane layer, which in turn is determined by the siloxane backbone andthe type of organic side groups it carries. Theoretically, most organicmolecules can be incorporated into siloxane side groups in variousproportions giving a huge range of potential surface chemistries, manyable to participate in yet further organic reactions.

It might be possible to divide the nature of the film into severalconditioning categories like these, and then describe individualsiloxanes, or groups or families of siloxanes, that provide filmsaffording that conditioning. At the moment, however, it is moreconvenient to discuss siloxanes generally, and then indicate what sortof effects films using them might permit.

Firstly, the siloxanes hereinbefore described as anti-lubricants alsoproduce strongly hydrophobic surfaces (on irons and steels) which forthat reason exhibits good corrosion resistance (specifically againstrusting conditions). This is particularly so for the lower molecularweight, and thus lower viscosity, dimethyl siloxanes several specificinstances of which have been identified above.

A wide range of poly(oxyhydrocarbyl) siloxanes, and specificallypoly(oxyethylene) siloxanes, provides layers having a significant waterwettability, and in the case of these poly(oxyethylene) siloxanes atleast this is strongly correlated with, and thus is a reliable indicatorfor, high adhesivity (it should noted, however, that this correlationappears not to hold for other siloxanes, such as the methylate glycineslike Goldschmidt 6950, which though providing a wettable surface reducesthe adhesivity of epoxies and cyano-acrylates almost to nothing). Thesepoly(oxyethylene) siloxanes can be used to provide a conditioned surfacewhich is a good base for epoxy-amine, cyano-acrylate,methyl-methacrylate and dimethacrylate-methanediol anaerobic adhesivesthemselves and for similar materials such as the numerouschemically-related paint resins, particularly the epoxy esters. In theselatter the establishment and maintenance of adhesion under environmentalexposure is a key to the corrosion protection performance of the system,but the corrosion performance is actually enhanced by the presence ofthe corrosion-resistance conditioning layer. Thus, the actual paintcoverage--that is, the thickness of the paint coating to provide a givencorrosion resistance--is reduced.

Typical instances of siloxanes that improve adhesivity are

Mazer (PPG) Chemicals SF19 an organofunctional siloxane of viscosity 45cSt, surface tension (1% aqueous) 20.4 dynes/cm. It is sold as asurfactant, and is thought to have a "tri-silicon" backbone (threesilicon atoms with trimethyl endgroups and a centralhydroxyalkyl-terminated poly(oxyethylene) pendant group: in some casesthe actual terminal group may be a hydroxy group).

OSi Specialties L77 a methyl-terminated nona(oxyethylene) polydimethylsiloxane of viscosity 20 cSt and surface tension (0.1% aqueous) 20.5dynes/cm. It is marketed as a surfactant, has a molecular weight ofaround 600, and has a tri-silicon backbone.

OSi Specialties L7607 a methyl-terminated poly(oxyethylene) polydimethylsiloxane like L77 but of viscosity 50 cSt, surface tension (0.1%aqueous) 23.4 dynes/cm, and a molecular weight of around 1,000.

OSi Specialties L7608 a poly(oxyethylene) polydimethyl siloxane like L77but with a hydroxyl terminating group. It has a viscosity of 35 cSt, asurface tension (0.1% aqueous) of 21.5 dynes/cm, and a molecular weightof around 600.

Th. Goldschmidt 5878 a methyl-terminated poly(oxyethylene) polydimethyltri-silicon siloxane wetting agent of viscosity 18-28 cSt, surfacetension (0.1% aqueous) 21 mN/m.

Th. Goldschmidt 5840 a hydroxy-terminated poly(oxyethylene) polydimethyltri-silicon siloxane wetting agent of viscosity 50-70 cSt, surfacetension (0.1% aqueous) 22 mN/m (this material has radically differentbehavior to the 5878 siloxane, and it is suspected that this is causedby the (unknown) chain length and terminator.

Slightly surprisingly, some of the siloxanes that produce water-wettablesurfaces also provide those surfaces with excellent anti-corrosionproperties (but see the remarks above about the Goldschmidt 6950betaine). It is not entirely clear how this effect is caused, but it isthought that, the siloxane coating being laid down with the siliconbackbone lying flat against the metal surface and the pendant sidechains projecting out therefrom (this is discussed further hereinafter),any water is trapped by the upstanding hydrophilic pendant layer, theunderlying hydrophobic silicon layer completing the barricade preventingthe water ever reaching the metal surface.

Oleophilic and oleophobic surfaces can also be formed. Thus, OSi L7500,a butyl-terminated poly(oxyethylene) polydimethyl siloxane with aviscosity of 140 cSt and a molecular weight of around 3000 makesoleophilic surfaces, while the fluorocarbon siloxane Dow Corning FS1265confers some slight oleophobicity.

One reason for producing a siloxane layer having lubricant rather thananti-lubricant properties is in the area of joint formation, where itmay be desirable to enable two metal parts being assembled together tobe slid into position one over the next with a reduced risk of gallinguntil the two are correctly positioned for making the galled joint. Asiloxane suitable for this lubrication purpose is Goldschmidt 5840.

Blending two or more different siloxanes may be desirable for a numberof reasons. For instance, a mixture of Mazer SF19 and a small amount(5-10%) of a 1,200 molecular weight 10 cSt DC200 had an increasedaverage molecular weight and so was more easily retained within itsrubbery siloxane carrier composition. Another blend example is one ofMazer SF19 and a small amount of a 100 molecular weight 10 cSt DC200,which showed considerably increased surface activity andwetting/covering power, and as a result formed a denser siloxane layer.Blends with an oxygen-scavenging methyl-hydrogen siloxane may beespecially useful for excoriating/conditioning uses.

Those siloxanes that have organofunctional pendant groups--that is, sidechains, that contain active groups (such as hydroxy, amino, or reactiveunsaturations, and so on, as aforementioned) able to take part in somechemical reaction--may have properties that are much like those of thecorresponding basic polydimethyl siloxane. However, if there is arelatively large number of such active groups then the properties of thesiloxane (or further-reacted siloxane) can be, or can be made, quitedifferent to those of the basic polydimethyl siloxane.

Shaping objects

In its second major aspect the invention provides a method of shaping anobject, in which the surface of the object is abraded away using acoarsely-abrasive tool (as aforesaid) to provide the desired shapedobject.

Although the shaping method of the invention could clearly be applied toobjects which are made of other hard materials, such as a ceramic orglass, nevertheless it is primarily intended for application to metalobjects, and for the most part that is how it is described hereinafter.

In the discussion of the possible tool types given hereinbefore much hasalready been disclosed about the method of using them to abrade andshape objects. Moreover, the Specification of our first aforementionedApplication (P1285) discusses abrading and shaping in some detail, andit is not necessary to repeat that at this time. Nevertheless, it mightbe useful to summarise the matter as follows.

The shaping method requires there to be caused significant rubbingfriction between the tool and the workpiece surface, and thus isparticularly useful in heavy duty applications such as plunge andcreep-feed grinding.

The method involves the surface of the workpiece being locally heatedand sheared by the continuing tool-derived frictional forces coupledthereto, which depend on tool speed; speeds in excess of 10 m/sec aresatisfactory for grinding but lower speeds are sufficient for lapping.

Conditioning surfaces

In another major aspect the invention provides a method of providing ametal part with a surface carrying bonded thereto a surface-conditioningsiloxane layer, which method is characterised by first excoriating thepart's surface under oxygen-excluding conditions and optionally in thepresence of a siloxane, to clean off the oxide film therefrom and toleave the metal surface bare and oxide-free, and then further rubbingthe bare metal surface in the presence of a siloxane in a substantiallynon-abrasive manner to form on the clean surface the desired layer ofsiloxane molecules individually bonded directly thereto.

So far, the invention has been described mostly in connection with whatmight be called the "bulk" removal of material from an object byabrasion, so as actually to cut into the surface and so shape theobject. However, as has been noted it is also applicable to thetreatment of a surface in which only the smallest amount of material isactually removed--possibly just enough to clean the surface of anyresidual dirt or corrosion or oxide layer thereon--and as such an aspectthe invention is a method of conditioning a surface for some subsequentpurpose. This concept--conditioning the surface for some furtherpurpose--is not disclosed or foreshadowed in the first above-mentionedApplication (P1285), and is now described in some detail.

Firstly, the types of tool employed for conditioning--the excoriatingtool--are those where there is used a flexible substrate (so as not totransmit too much force to the tool as it rubs over the surface) and avery fine abrasive (so as to keep the possible abrasion down as far aspossible). A flexible, soft tool is more able to follow the contours ofthe surface and so reach into dips or troughs therein and therebyprovide better coverage.

Secondly, the reasons for carrying out the conditioning--the benefitsexpected as a result thereof--are diverse. More specifically, thesurface might be conditioned to instil and retain for future use themobile siloxane layer as: a plastic lubricant for running plastic orrubber seals against; a metal-to-metal boundary lubricant; ametal-to-metal anti-lubricant (the very opposite of a lubricant) forconferring on the part the ability to make galled joints; ananti-corrosion layer for keeping water or other corrosive liquids offthe metal surface; a water- or oil-wetting agent; a keying layer towhich a subsequent layer of adhesive or paint would strongly bond; acatalytic layer able to participate in some further reaction; or as apassivated layer to achieve environmental, for instance bio-,compatibility.

In order to prepare the siloxane-coated surface the relevant area of themetal part's surface is first excoriated in the presence of a siloxane,and is then further rubbed in the presence of the same or a differentsiloxane. The primary reason for the presence of the siloxane during thefirst stage is because it serves to keep ambient oxygen away from thecleaned, oxide-free surface (this may be by it forming a physicalbarrier and/or as a result of its oxygen-scavenging ability). Inaddition, it also initiates the formation of the desired bonded siloxanelayer onto that surface (this formation subsequently being completed inthe second stage).

The preparation involves cleaning the metal surface by the removaltherefrom of any dirt and oxide film thereon (it will be understood thatthe surface thus rubbed and cleaned is that portion or area of thesurface on which it is required to form the siloxane layer; this may beany amount ranging from the whole to only a small but neverthelesssignificant fraction of the metal part's area). This cleaning is amechanical process; the dirt, oxide and other surface contamination aresimply scraped off, and moved away to one side, leaving bare, "pure"metal behind. In fact, some metal is likely also to be scraped off, butit is not the purpose of the conditioning method to remove anysignificant amounts of metal--this aspect of the invention involves notshaping the surface, merely cleaning it--and so too much abrasion,either inherently or with time, which produces large amounts of swarfthat are difficult to remove without admitting more free oxygen, is tobe avoided (once the surface is clean, that is enough). That having beensaid, a very small amount of metal removal--smoothing away the tips ofthe surface's microprojections--is bound to happen, and may bebeneficial in that it reduces surface roughness.

The bare metal surface produced is highly reactive; it needs to beprotected from ambient oxygen--or, indeed, other reactive contaminantmaterials--and that is what the siloxane present does, both by creatinga physical barrier and by being an oxygen scavenger. The conditioningmethod of the invention first excoriates in the presence of a siloxaneand under oxygen-excluding conditions, and then further rubs it again inthe presence of siloxane. Doing the excoriation under oxygen-excludingconditions (necessary to reduce the possibility that ambient oxygenseeping back onto the cleaned metal surface could replace the oxidelayer as fast as it is removed, and so prevent the direct bonding of thesiloxane molecules) can be effected in a number of ways. One, obviously,is to carry out the operation in the actual absence of oxygen--in aninert atmosphere (of nitrogen or an inert gas, say), and this might beappropriate in some cases. A much simpler way, however, is to excoriatethe surface, and apply the siloxane, using a rubbing, abrasive tool thatcompletely covers (or masks) a relatively large area at a time, and ismoved (to rub) in small circles or zigzags that gradually translocateacross the surface (like one polishes a table or a car); in this way thecentral area that is being cleaned is always surrounded by tool-bearingsiloxane that itself provides both a mechanical and a chemical barrierto the ingress of ambient oxygen, and by the time the tool has movedaway from that area the bare metal has already acquired its siloxanelayer.

Once the preliminary cleaning stage is over the thus-cleaned surface isfurther rubbed in the presence of siloxane such that there is formeddirectly on the surface a siloxane layer made up of siloxane moleculeseach individually bonded to the underlying metal. Usually, this "secondstage" will be a seamless continuation of the first stage; as notedhereinbefore, the mildly-abrasive rubbing in the presence of a siloxanecauses initiation of siloxane-layer formation, as the siloxane presentbinds to the exposed clean metal surface as it is formed. It may,though, be the case that this subsequent rubbing is conducted as adistinguishable, separate, stage--for example, the cleaning abrasion ofthe oxide-covered metal surface may be effected with an abrasiveflapwheel (and a first siloxane), and immediately thereafter the clean,oxide-stripped surface may be rubbed with a cloth soaked in (possibly asecond) siloxane. A second, different siloxane might be used when thedesired conditioning effect is only provided by such a siloxane that isnot itself satisfactory for use in the preliminary oxide-film-removalexcoriation stage. For example, the excoriation is best effectedutilising a thin, mobile siloxane, but the required conditioningsiloxane might only be available as an unsuitably thick, viscousmaterial (which is applied after cleaning the excoriated surface of anyresidue of the first stage).

It is not entirely clear how the conditioning siloxane bonds to thecleaned underlying metal surface, nor how it confers on that surface therequired properties. As to the former, though, it is thought that oncethe starting oxidised metal surface has been cleaned by abrasive actionto reveal the underlying metal, which is chemically unstable, with manybroken interatomic bonds and so is extremely reactive, then theindividual molecules of the free siloxane preferentially bond to thethus-cleaned surface in place of any remaining oxygen in such a way thatthe siloxane's silicon-oxygen chain ( . . .--Si--O--Si--O--. . . ) liesflat across the surface, with its oxygen atoms adjacent and linkedthereto, while the side groups project up out of and away from thereactive surface, and are screened therefrom by the silicon atoms.

The formed siloxane layer has significant effects. For example, it isthought that other functional materials can be chemically reacted tothis bonded layer as a means of creating and controlling surfaceconditions even further. For instance, it would be possible to react afurther chemical to the siloxane's pendant chain terminal groups if carewas taken to ensure appropriate functionality, this second-reactedchemical possessing other "functionality", possibly a hydrocarbon chain,to provide lubrication properties or anti-corrosion properties, or somesort of bio-compatibility.

This type of modified surface, in which siloxane is directly bonded tomost of the substrate material so that the normal behavior of thesurface (which is due mostly to the all-covering natural oxide layer) isradically altered, is believed to be unique. It is believed, moreover,that a surface treated by this method will retain the siloxane bondsindefinitely if kept away from those chemicals, such as some acids andbases, known to attack siloxanes. Hence it should be possible to treatsurfaces during manufacture for later functional use--perhaps severalyears later--or to provide surfaces with an effect such asfriction-enhancer functionality guaranteed for life. On iron and itsalloys the siloxane's action is likely to result in the formation ofsome iron silicates, known for their tenacity when bonding to iron oxidesurfaces, but it is believed the bulk of the deposited silicaceousmaterial will remain as a polymer that is chemically, or polar, bondeddirect to unreacted iron, and is therefore available to provideconditioning.

In this connection it has been noted that finely-abraded iron surfacesprepared using a paper with an abrasive-loaded absorbed rubbery siloxanecomposition do have a significantly improved resistance to oxidativecorrosion (rust). Preliminary tests have shown this resistance to beeffective against condensed water droplets, and to a lesser extentagainst brine and hydrochloric acid attack. The concept described hereof using a mild abrasive to disrupt oxide layers to allow intimatebonding (plating-on) of a protective water-repellent layer of siloxanesseems attractive as a potential method of treating many surfaces as analternative to the chemically-polluting electroplating systems commonlyused at present. In particular, it has been observed that, after wipingclean after abrading, the surfaces appeared to retain theirwater-repellency and corrosion-resistance features indefinitely.

The conditioned metal surface per se

Finally, one further facet of the invention is the metal partsthemselves carrying the siloxane layer thereon, and so in this aspectthe invention provides a metal part with a conditioned surface havingsiloxane molecules each individually bonded directly to the metal over arelatively large area of the surface to provide a relatively uniformsiloxane layer.

Although this aspect of the invention is discussed in more detail below,it would seem desirable first to explain why such a concept--metalsurfaces with a siloxane layer thereon--is believed to be both novel andinventive despite a wide variety of Art relating to the formation ofsilicone coatings on metals.

It is common to apply silicone polymer films to a metal surface. Indeed,it is known to polymerise the monomeric materials directly at thesurface for the purpose of providing the surface with improved ordifferent properties (such as being corrosion-resistant or a good paint-or adhesive-base). However, for the most part all these prior siliconepolymer layers have been formed on, and adhered to, the oxide layeralready present on the metal surface (indeed, in many cases they aredesigned specifically to interact with the oxide layer, this supplyingthe tie between the polymer and the underlying metal). The adhesion ofthe polymer layer to the oxide layer, and thus to the underlying metal,is not always as good as might be hoped, and in a related situationwhere adhesion-promoting silane layers are said to be formed on metalsvia the oxide-layer the latter has been described as being partially(chemically) etched off--but by partially is meant that over its entireextent it has been thinned by the etching process, so it still coversthe entire metal surface but is not as thick (and perhaps now lacks thelooser upper layers) as it started out, so that the silicon material isstill, but more firmly, attached to oxide and not to metal. Such layersattached to a thinned oxide layer are said to adhere better than thosewhere the oxide layer has been left alone.

A case of silicone-polymer-layer-attachment arguably not via the oxidelayer is where the oxide layer has been partially removed buthaphazardly, and quite by accident, in small areas spaced randomly overthe surface; this appears to be the case where siloxane lubricants inbearings are described as having failed under extreme conditions,allowing the bearing to seize (subsequent examination of the seizedsurfaces revealed that they carried a thin film of silicone polymerapparently adhered directly to the underlying metal, but this layer wasin very-small-area patches distributed non-uniformly over limited partsof the surface).

In the Specification of our first aforementioned Application (P1285)there is described and claimed a method of shaping a metal workpiece byremoving material from its surface, in which method the surface of theworkpiece is continuously "rubbed" by a tool in a friction-inducingmanner and in the presence of a friction-enhancing agent in a quantityand in a form such that actual friction enhancement occurs, and at leastsome of the surface material in frictional contact with the tool issheared from the workpiece surface by the continuing motion of the tool,and discarded. The whole purpose of this method is to remove material,and there is no interest in the nature of the surface, or any layerformed thereon, save that during the material-removal oxygen should beexcluded from the surface at the tool/surface interface.

The Specification discusses what takes place in the immediate area oftool/workpiece contact--that very small area in actual rubbing contact.What happens is that, in the presence of a friction-enhancing silicone,the inevitable oxide layer is first mechanically disrupted to revealbare metal--this is thought to occur simultaneously with the thermaldegradation and physical breaking of silicone molecules "trapped" in thecontact area into smaller moieties which themselves have anoxygen-scavenging capability and so react with any available oxygen toprevent it attaching to the bare metal surface and reforming the oxidelayer (the greater the tool/workpiece contact forces the more extensivethe formation of the desired oxygen-scavenging moieties)--whereupon thetool microwelds to a myriad of microscopic areas of the bare, oxide-freesurface (this microwelding is more extensive than it would be withoutthe oxygen-scavenging action of the silicone), and its subsequentmovement then necessarily tears minute slivers of metal off theworkpiece. Once the tool has moved on, taking the torn-off metal withit, there is left, for a very brief instant, a corresponding tiny areaof bare metal--but that instant is brief, being of the order ofmicroseconds, because, in the absence of any positive attempt to excludeambient oxygen from the surface, the bare patches are almostinstantaneously and preferentially re-covered in an oxide layer.

It might be thought that, the metal-tearing rubbing having been effectedin the presence of a silicone, this renewed onslaught of ambient oxygenwould be resisted. However, in the circumstances of the metal-shapingoperation of this prior Specification such is not the case. While it isbelieved that the silicone moieties generated by the tool's physicalbreaking-down of the silicone molecules have oxygen scavengingproperties, this is not--or does not seem to be--the case with thesilicones themselves; they have no significant oxygen scavengingcapability. Moreover, while there may be some "unused" siliconebreakdown products left behind adjacent the bare metal revealed as thesliver is torn off, in the absence of any positive steps to excludeambient oxygen from the site these are unable, or insufficient, toprevent that relatively reactive oxygen flooding onto the bare metal andre-forming the oxide layer. And in this context it is worth noting thatthe silicone materials used in such a metal-shaping method are usuallyrich in dissolved oxygen, and may even be supplied to the site by aphysical process which causes oxygen to be entrained (such as the normaluse of a water-based flood coolant for a grinding wheel).

It should be appreciated that under the conditions of the metal shapingmethod of this prior Specification at no time is a siloxane layer formedanywhere bonded directly to the metal surface--and specifically not onthe formed clean, bare metal patches.

In the Specification of our second aforementioned Application (P1220)there is described and claimed the formation of galled joints by amethod involving the application of gall-promoting--that is to say,anti-lubricant--siloxanes to opposed metal surfaces which are thenbriefly rubbed together to cause random gall formation which binds thesurfaces together (and so forms the joint). It is likely that duringthis brief gall formation there is some haphazard and incidentalsiloxane-layer creation as the gall-producing metal is transferred fromone opposed surface to the other, revealing fresh clean metal which isthen exposed to any remaining siloxane. It is even possible that theremay briefly and fortuitously be produced an uneven layer of siloxaneactually bonded onto the metal surface. However, this siloxane layer, ifit occurs at all, is transitory in the extreme, being in existence formerely the few milliseconds necessary for the joint to be made. It isquite different from the long-term, uniform, dense, large-area siloxanelayers the subject of the present invention. The conditioned-surfacemetal part of the invention is quite different; the metal surface hasthe siloxane molecules individually bonded directly to the metal over arelatively large area of the surface to provide a relatively uniformsiloxane layer systematically controlled.

This final facet of the invention is the metal parts themselves carryingthe siloxane layer thereon--a metal part with a conditioned surfacehaving siloxane molecules each individually bonded directly to the metalover a relatively large area of the surface to provide a relativelyuniform siloxane layer.

As will be clear from what has gone before, the metal part may be ofalmost any sort depending upon its purpose and the purpose of applyingthe siloxane coating. Thus, it may be a sheet of steel which is to begiven an anti-corrosion paint-adhesion layer, or it may be a part of ajoint--an axle, say--to be galled to some other part--a cam or gearwheel. Or it may be a length of strip that is eventually to be glued tosome other object, and so requires an adhesive-base conditioning layer.In each case the formed siloxane coating will need to cover a relativelylarge area of the part, and will need to be uniform thereover.

The siloxane will be chosen for the properties it can confer. This, andthe chemical nature of the siloxane, has already been discussedhereinbefore, and needs no further comment here.

EXAMPLES

The following Examples are now given, though by way of illustrationonly, to show details of the various aspects of the invention.

A primary objective is to provide an abrasive composition of arubber-like carrier compound in which a low molecular weight, relativelyfree siloxane is retained, trapped but capable of being released onto asurface either of a tool or of a workpiece treated using that tool, andwetting that surface. The carrier matrix must be able to hold thesiloxane indefinitely both in storage and in use without it leaching orcreeping out beyond the treated area of the tool. A second objective isto provide a tool to which the composition has been applied, and to usethat tool in a shaping or excoriating/conditioning method. A thirdobjective is to form differently-conditioned surfaces using one or moreof a range of siloxanes.

Shaping compositions and tools

Example 1 Preparation and Use of a Composition for Treating a GrindingWheel

The rubbery friction-enhancing agent composition

At room temperature a 150 ml mix was prepared in the followingproportions by volume:

20% Masil 28 (a copolymer material comprising principally polydimethylsiloxane with about 80 monomer and about 4 monomers with reactive acidanhydride side groups)

25% Dow Corning 109 (a fairly long chain polydimethyl siloxane withreactive hydroxyl end groups)

50% Dow Corning 200/100 (a non reactive linear polydimethyl siloxane toact as the free slow release friction-enhancer)

To this was added a 5% stannous octoate to catalyse the mixture.

The abrasive

5 grams of 320 grit fused alumina were brushed evenly over the surfaceof a 200 mm diameter by 20 mm deep Norton 38A46LVS wheel, brushingtowards its outer rim, and then vibrated into the wheel using apneumatic hammer.

Applying the composition

The siloxane mixture was then poured onto and spread evenly over thesurface of the wheel. Both sides of the wheel were coated, and theentire mix was easily absorbed into the porous structure of the wheel.The composition appeared to cure to a soft rubber in less than 2 hourswithin the wheel.

A separate sample applied to a open flat glass surface actually cured toa stiff rubber in less than 30 minutes.

Tests

A simple comparative grinding test was performed comparing anabrasive-composition treated wheel (wheel A) with both an untreatedwheel (wheel U) and a wheel treated only with the siloxane composition(without the abrasive: wheel S).

On test against soft steel wheel S was seen to show the characteristicbehavior of a siloxane-treated wheel (as detailed in our firstaforementioned Application P1285!) of cutting rather faster thanuntreated wheel U, and of removing more metal per dressing. For wheel A,for grinding a soft metal specimen there was no difference inperformance over wheel S. However, on grinding a hard specimen thereappeared to be an improvement in grinding efficiency; the higher thewheel load (force of workpiece pushing against wheel), the greater theimprovement in metal removal rate.

Example 2 Preparation and Use of an Alternative Composition for Treatinga Grinding Wheel

The rubbery friction-enhancing agent composition

At room temperature a 150 ml mix was prepared in the followingproportions by volume:

10% Masil 28 (a copolymer material comprising about 80 monomer units, 4of which are said to have reactive acid anhydride side groups, theremainder being passive dimethyl and using methyl terminal groups)

20% Dow Corning 109 (a fairly long chain polydimethyl siloxane withreactive hydroxyl end groups)

10% Rhone Poulenc V48/100 (a low viscosity polydimethyl siloxane withreactive hydroxyl end groups)

(Note that the proportions of these hydroxy materials determine thehardness of the cured rubber--the higher the 109 the softer the rubber).

55% Dow Corning 200/50 material (a passive polydimethyl siloxane for useas the friction-enhancer)

5% Stannous Octoate (to act as a catalyst)

The abrasive

As in Example 1, 5 grams of alumina 320 grit powder was vibrated in to aNorton 38A46LVS wheel.

Applying the composition

The prepared rubbery composition mixture was applied as before to thewheel. It appeared to cure in the wheel in less than 2 hours, and wasdry to the touch on an flat glass surface after 45 minutes. The materialgave a slightly stiffer rubber than those in Example 1, and appeared toprovide a greater siloxane feel to the actual grinding surface of thewheel.

Tests

On test this was seen to perform similar to the wheel of Example 1.

Example 3 Preparation and Use of an Abrasive-Loaded Rubber for MouldingInto a Tool

The rubbery friction-enhancing agent composition

At room temperature the following mix was made, all measures being byvolume:

8% Masil 28 (the copolymer described in Example 1 above)

16% DC109 (as described in Example 1)

8% RP48V/100 (a polydimethyl siloxane with linear chains and reactivehydroxyl end groups))

46% DC 200/100 (as friction-enhancer, as in Example 1)

18% fused alumina powder 320 grit size

4% tin octoate (as catalyst)

The above was mixed thoroughly, and when the reaction was clearlyestablish, as evidenced by many small bubbles and after about 10 minutesmixing, it was poured into a mould. It took about 4 hours to cure.

After leaving for about 24 hours the cure appeared complete because therubber was dry to the touch and failed to gain further strength.

The formed tool could be used for lightly abrading a steel surface. Thetool actually wet the surface with siloxane, and deposited a quantity offine abrasive on the surface also. Hence, this tool is suited to eitherwetting another tool by allowing it to run against it, like a linisherbelt, or as part of a two-part tool system where this tool prepares thesurface by coating a surface with the friction-enhancer and abrasiveready for final polishing off with a dry buff.

Example 4 Preparation of a Grinding Wheel Shaping Tool.

Stage A: Preparation of an (abrasive) composition

At room temperature a particularly preferred mix was prepared asfollows:

30 ml 48V50 or 48V100 for slightly tougher rubber (Rhone Poulencsiloxanes)

75 ml 200/50 (Dow Corning siloxane)

20 ml 200/10 (Dow Corning siloxane)

20 ml Y-11343 slow cure/soft; A-1120 fast cure/hard (silanes from OSiSpecialties)

5 ml stannous octate (polymerization catalyst)

(the constituents may be varied as shown to adjust the rubber to suitthe application; all the rubbers are deliberately weak so they do notball up and wedge under and lift the tool off the work-piece at lowcontact forces). The materials were mixed thoroughly to give a fluidcomposition with a shelf life dependent on the particular silanecross-linker (six hours for the Y-11343; about 30 minutes or less forthe A-1120).

The result was a rubbery friction-enhancing agent composition that inuse rapidly decomposes at the abrading surface to prevent toolwork-piece separation.

Stage B: Preparation of a shaping tool

5 grams of 320 fused alumina grit were vibrated into a Norton 38A46LVSgrinding wheel evenly within a 25 mm band near its periphery. The mixedcomposition was then poured onto the grinding wheel (held horizontally)which absorbed it completely, and allowed to cure at room temperature(this took about 24 hours and 1 hour respectively).

Alternate Stage B: Preparation of other shaping tools

The same composition was also used to provide a grinding disc and alinishing belt with a secondary abrasive surface, in accordance with theinvention. First, the disc or belt was dusted with 320 fused aluminagrit mixed with 1% by weight Degussa Aerosil 200 (fumed silica: athickening agent present to cross-link the siloxane and so strengthenthe rubber in the valleys between abrasive on the disc or belt surface).

Grinding test

The formed grinding wheel tool of the invention was then used to cutinto mild and hard steel test specimens, and compared in this with anuntreated wheel and a wheel as treated in accordance with the inventionthe subject of our aforementioned International Application (P1285).Both treated wheels were comparable on mild steel and at low loads tothe untreated wheel, but were significantly better as the loadincreased. Moreover, on hard steel the present invention's toolperformed considerably better than that of the previous one.

Similarly beneficial results were achieved when using a grinding disc ofthe invention.

Example 5 Preparation of a Grinding Disc Shaping Tool

Stage A: Preparation of a gel-like rubbery abrasive composition

At room temperature, a pre-mix of

2.5 ml Masil 28 (PPG/Mazer siloxane), and

2 ml DC1107 (Dow Corning siloxane)

and a pre-mix of

1 ml RP21637 (Rhone Poulenc siloxane) and

2 ml DC1107 (as above)

were sequentially added to 1 ml DC1107 in a beaker and blended in for 1minute. 0.5 ml water was then added, and the whole was stirred for afurther minute. At this stage the resulting composition was a milkysemi-viscous liquid.

Stage B: Preparation of the shaping tool

70% of the contents of the beaker were then poured onto an 180 mmdiameter coated abrasive disc that had previously been lightly dustedwith 0.5 g fused alumina 320 grit, and spread evenly over disc surfaceby brushing in with a small paint brush and left for 24 hours to cure.At that time the composition was tacky.

The material left in the beaker became a solid gel after four days; thedisc was still tacky after seven days, but eventually became dry to thetouch.

Tests

A simple comparative abrading test was performed contrasting theabrading rate of the treated disc shaping tool against an untreated discoperating under identical conditions.

The torque load was progressively increased by increasing the rubbingpressure of the tool against the workpiece. At low loads there was noperceptible difference between the treated and untreated discs, but asthe contact pressure increased so the torque load rose more rapidly onthe treated disc. At the point where the drive was just able to maintainits rated operating speed, it was found that the treated disc removedsoft steel at a rate 30% higher than that attained by the untreateddisc; it was also found that the drive current required (for theelectric motor driving the disc) at this cutting rate was between 10 and15% higher for the treated than the untreated wheel operating at thesame rubbing contact pressure.

Excoriating compositions and tools

Example 6 Preparation and Use of Abrasive Paper Wipes

The rubbery friction-enhancing agent composition

The mix was prepared using the formulation detailed in Example 3 above.

Approximately 5 ml. of mix was poured onto a strip of 80 g/mm² Absorbexpaper (50 mm.×250 mm.) supplied by Laminating Papers Ltd Kanavaranta 1,SF-00160 Helsinki, Finland. This was spread evenly over one side only,and the fluid soaked into the paper leaving most of the abrasive on thensurface.

The strip was left to cure for about six hours, after which it could beused as an effective excoriation tool.

Tests

Evidence of its effectiveness at metal oxide removal was seen by therapid discoloration as iron oxide rapidly turned the surface black. Thewipe would leave a smear of friction-enhancer on the surface togetherwith a scattering of fine abrasive. By turning the wipe over and usingthe side without abrasive the surface could be further polished. Againthere was clear evidence of oxide removal, because the wipe side withoutabrasive actually discoloured black when the surface had previously beenpolished with the abrasive side. However, save for the removal of somesurface dirt when the abrasive free side was rubbed against a new steelsurface, the side without the abrasive barely marked the surface (theremoval of the dirt was attributed to the wetting effect of the releasedsiloxane from the soaked wipe acting as a degreaser).

Example 6A Preparation of a Mild Steel Surface with Improved CorrosionProtection

A 75 mm×50 mm cold rolled mild steel plate was degreased and wipedclean. The surface was without any sign of corrosion.

A wipe, as prepared in Example 6 above, was used to polish half thesurface of the plate. Polishing was done by hand with only lightpressure, first using the abrasive coated side of the wipe for abouthalf a minute and then with the uncoated side of the wipe for about halfa minute. The polished surface was then wiped to remove remnants ofpaper, abrasive and surplus friction-enhancer.

The polished surface appeared dull grey, and was in fact was less shinythan the unpolished cold rolled original surface.

Tests

The plate was then half immersed in domestic tap water for 2 hours, thenremoved and allowed to dry.

Rust pits developed around the drying areas on the untreated surface,but the abraded surface showed no sign of corrosion. After 10 daysstanding in the open laboratory there was still no sign of corrosion onthe treated surface, while the untreated surface had become quite rusty.

The experiment was repeated using water with 1 wt % sodium chlorideadded, and this showed much more aggressive corrosion (rusting andstaining) of the untreated surface, while the treated surface showedstaining with drying marks, and a few tiny rust pits that did not growbeyond pin head size. After two weeks in the open air the untreatedsurface was completely covered in red rust, whereas the treated surfacewas still 50% clear of corrosion.

The experiment was repeated using water with 5% hydrochloric acid (28°TW) added. The surfaces above the water corroded within 5 minutes due tothe vapours released. The treated area appeared to be a lighter red andwith a much finer texture than the untreated, and the severity ofcorrosive attack appeared less on the coated area. The immersed sectiondid not significantly corrode on either the coated or uncoated section,but the treated section appeared to have a light and more natural steelcolour than the untreated. It looked as if the untreated surface hadstained.

There were signs of slight rust developing after two weeks standing inthe open laboratory, around dry marks on both of the immersed sections,these dry marks being from a water wash to remove residual acid.

Thus, it was established that by abrading a steel surface by the methodof the invention the risk of minor corrosion due to fresh water attackis much reduced. Salt water corrosion is slightly reduced, and acidresistance is changed.

Example 7 Preparation and Use of a Laminated Paper Abrading Tool

The rubbery friction-enhancing agent composition

A liquid formulation was prepared as in Example 5 above. It was thenused to treat six strips (50 mm.×250 mm.) of 30 g/mm² Absorbex paper (3ml of liquid were applied evenly to one side of each strip, and allowedto soak in).

The strips were then placed on top of each other to form a laminatedboard which was then gently pressed into what ever tool shape wasrequired (in the case of the proving sample it was pressed flat).

After curing for about four days the board became relatively stiff andcould be used initially without backing, as an abrasive tool.

Tests

At least four of the six layers were worn away in the experimentaltrials, and the tool was still releasing an adequate supply of abrasiveand friction-enhancer.

The test was repeated with a steel backing plate bonded directly to thelast layer using the gel-like friction-enhancer carrier as the bondingmedium. This back plate bond proved to have adequate strength towithstand the shear loads imposed when hand-abrading flat mild steelsurfaces.

Example 8 Preparation of Paper and Cloth Excoriating and ConditioningTools

Stage A: Preparation of an abrasive composition

At room temperature the following mix was prepared:

1.5 ml 48V50 (Rhone-Poulenc siloxane)

4 ml SF19 (Masil PPG hydrophilic, lubricant, siloxane) or 200/50 (DowCorning hydrophobic, anti-lubricant, siloxane)

1 ml 200/10 (Dow Corning siloxane)

0.5 ml A-1120 (OSi Specialties silane)

4 drops stannous octoate (catalyst)

These were all mixed together, with stirring. The result was a rubberycomposition, suited to retaining low molecular weight conditioningsiloxanes and anti-lubricant siloxanes, that also acted as an adhesiveto retain abrasive particles on a surface.

Stage B: Preparation of a paper conditioning (excoriating) tool

The formed composition was applied to 10 different 80 gm2 Absorbex Kraftpaper strips 25 mm wide by 280 mm long from Laminating Papers Ltd.Kotka, Finland.

Each strip was first lightly dusted with a layer of dry 320 gritabrasive white alumina powder admixed with about 1 wt % Degussa Aerosil200 fumed silica (to add strength to the rubber layer bonding theabrasive grains to the surface). The actual amount of abrasive usedshould be chosen to be that appropriate to the subsequent use of thetool; for hand tools only the lightest dusting is needed, and this wassimply achieved by sweeping a small amount of the abrasive mix acrossthe surface with a small brush so that the abrasive filled theundulations in the surface.

The siloxane mixture was then poured as a thin line down the centre ofthe strip, and allowed to soak out towards the edge (it is advisable todo this with the strip horizontal on a non-absorbent surface to preventthe low molecular materials seeping out before the rubber cures). Therubber cured in about 1 hour; the paper was stretched horizontally androtated slowly whilst soaking and curing.

Alternate Stage B: Preparation of a non-woven cloth conditioning(excoriating) tool

Carrying out the invention with non-woven cloth makes a similar productexcept that more rubbery composition is absorbed, and the surfaceundulations being larger it traps more abrasive. Hence, a tool made withsimilar size strips of HWC 35 or HWC 50 (light, and slightly heavier,grades of 80% polypropylene/20% cotton blends supplied by Bonded FibreFabric Ltd. Bridgewater, UK), lasts longer and has greater physicalstrength due to the stronger material (though care must be taken here toorientate the strip along the axis of the material weave with thehighest strength and least extension).

Tests

1. Test for anti-corrosion conditioning

A degreased metal plate 100×75 had half its surface excoriated with anSF19 paper wipe (the hydrophilic one) for one minute, and was thenwashed in ICI EVOLVE CH15 (a volatile blend of hydrocarbon solvents) anddried, then subjected to a corrosion test of 10 cycles of wetting anddrying with rain water. After this, 80% of the untreated area wascovered in rust while only 5% of the treated areas was rusted. Thesurface was hydrophilic, and wetted fully.

A further paper wipe prepared with Dow Corning 200/50 material (ahydrophobic anti-lubricant) in place of SF19 showed similar corrosionproperties. This surface was hydrophobic, and showed high water dropletcontact angles of the order of 90°.

2. Test for lubrication and anti-lubrication behavior

In a further test two similar paper wipes were tested for theirlubrication (SF19) and anti-lubrication (DC200/50) properties. A batchof twelve mild steel hubs 10 mm deep were machined with an outsidediameter of 35 mm and a bore of 18 mm. A set of matching shafts 50 mmlong was prepared with a nominal interference fit of 15 microns.

Two shafts were washed in ICI CH15, and dried before being forced,otherwise untreated, into hubs--so the end of the shaft was flush withthe hub face--with an average assembly force of 24 kN. A second twoshafts were similarly washed, then smeared with DC200/50, and thenwashed again to remove any material not actually bonded to the surface,and then assembled into their hubs with an average 24 kN (no difference,as might be expected).

Another four shafts (and bores) were excoriated with lubricating SF19wipes, then they were thoroughly washed with more CH15 (to remove anyunbonded siloxane and loose abrasive grains), and then forced together.The average force required was 21 kN, a reasonable decrease showing thatthe surfaces had been given some lubricating conditioning.

A third set of four shafts (and bores) were excoriated withanti-lubricating DC200/50 wipes, and then forced together. The averageforce to assemble these was 63 kN, this showing a considerable increasein friction due to the anti-lubricant surface-conditioning action.

Example 9 Conditioning Metal Surfaces

This Example concerns the conditioning of metal surfaces for variouspurposes--such as improving adhesion of glues and paints thereto, andfor providing enhanced corrosion resistance--and using various differentappropriate types of siloxane. The Tests then carried out werecomparisons between the intended (conditioning) effect--adhesion,say--of a dry clean abraded steel surface and that of similar surfacesafter excoriation with one of 16 different siloxane formulations.

Adhesion Test

In this Test two metal plates are stuck together in a nominally 10 mmoverlap along one edge.

Two 18 swg mild steel plates (100×75 mm) were degreased in CH15, andwiped dry. A strip between 10 and 25 mm wide was excoriated across one75 mm edge, using a wooden block with a flat 10×'mm face around whichwas wrapped Norton Durite T426 abrasive paper with P400-A grit. A fewdrops of the appropriate conditioning fluid--see the Table below--wereplaced on the surface and gently rubbed into the surface with aprogressive circular motion of the excoriation block. After about 30seconds the surface was covered in a blackened liquid, evidence thatmuch oxide had been removed; this was wiped off with a dry paper towel,and the surface was then washed in CH15 and dried.

Adhesive (see below) was applied to each excoriated surface, and thesewere placed in contact with overlaps of about 10 mm, and firmly clamped,the overall assembly then being 190×75 mm.

One of the adhesives used was an epoxy resin glue--it was a two-packepoxy-amine similar to Ciba Polymers 2012, a rapid cure general purposeadhesive. The other was a cyanoacrylate glue--it was Loctite Super Glue3 (based on an ethyl-2-cyanoacrylate). All the epoxy specimens weregiven a 24 hour room temperature cure, and all the cyanoacrylatespecimens were given a 4 hour room temperature cure.

The glued metal sheets were then subjected to the well-known peeltest--that is, a controlled attempt was made to lever them apart (one isheld stationary while an increasing force is applied to the free edge ofthe other in a sense to lever it away from the one). The peel test wasadopted because it is an easily-reproduced means of comparing therelative adhesive strengths of joints in tension (this test is believedto be less influenced by small differences in surface roughness betweenspecimens than is the other standard tensile shear test, in which thetwo plates are pulled apart in a sliding sense).

For the particular version of the peel test used here, on the assembledjoint one plate was clamped horizontally and securely between steel jawsat the edge of a bench, and a weight was hung off the end of theprotruding "under" plate 100 mm from the jaw edge. The weight wasprogressively increased until the joint yielded. The distance of the topof the overlap from the jaw edge was measured, and the peel strength wasthen calculated.

Corrosion Test

In this Test treated metal plates are allowed to get rusty.

One half of the surface of a similar 100×75 mm steel plate wasexcoriated and treated (in exactly the manner described above, and withthe same range of materials) for about 1 minute, then wiped clean andwashed as above in CH15. The complete surface was then wetted with rainwater, and left to dry. This was repeated 10 times, and then thepercentage area covered in red rust was estimated. The results in theTable below compare the treated half of each plate with its untreatedhalf.

                                      TABLE    __________________________________________________________________________                    Average values & % change over 5 tests                    Adhesion        corrosion                    Epoxy   Cyanoacrylate                                        Rust    Test        Silicone    Peel    Peel        % cover    No: Conditioning Material                    N/mm                        % Chg                            N/mm                                % Chg                                    Before                                        After    __________________________________________________________________________     1) Comparative Conditioned                    4.9 --  3.7 --  --  --        Surface        (Dry Abraded Surface)     6) Polydimethyl-linear                    --  --  4.2  +13                                    75  10        DC200/50     7) Methylhydrogen-linear                    --  --  4.3  +16                                    75  5        DC 1107        Aminofunctionals-linears     8) RP 1300 (monoamine)                    --  --  4.0  +8 --  --     9) RP 21637 (diamino)                    --  --  3.8  +3 85  5    10) Amino Silane-        OSi Y11343 X-linker                    --  --  4    +8 --  --    11) Organofunct. silane blend        OSi Y11597 X-linker                    --  --  6.6  +78                                    --  --    12) Acid Anhydride copol-        Masil 28    --  --  9   +142                                    --  --    13) Alpha/Omega modified        linear organic wetter        Goldschmidt3130                    --  --  10.3                                +189                                    65  35        Polyethylene Glycols    14) Goldschmidt 3020 (OH)                    8   +63 6    +62                                    --  --    15) Goldschmidt 5840 (OH)                    6.7 +37 4.8  +30                                    65  65    16) Goldschmidt 5878 (Me)                    9.1 +86 9.3 +151                                    65  5    17) OSi 7607 (Me Terminal)                    9.3 +90 9.8 +165                                    85  8    18) OSi 7608 (H Terminal)                    10.3                        +110                            10.7                                +189                                    80  30    19) OSi L77 (Me Terminal)                    9.7 +97 8.6 +132                                    --  --    20) Mazer PPG SF19 (HO)                    6.4 +31 7.8 +111                                    80  1    __________________________________________________________________________

There are two groups of results here. First is a group (Tests Nos: 6 to13) where the reacted layer significantly improves both cyanoacrylateadhesion and corrosion resistance, and the second group (Tests Nos: 14to 20) shows a clear trend for polyethylene glycol siloxanes to increasebond strength with both epoxy amine and cyanoacrylate adhesives, andalso in most cases increases corrosion resistance. In each case thevariation in bond strength shown is greater than any experimental errormight be, so this result clearly demonstrates that a reacted siloxanelayer radically affects surface adhesion.

The variations in adhesion between the siloxanes is mainly attributed tovariation in pendant length and structure and to a much lesser extentthe terminal molecule. There is evidence that the materials withOH-terminated caps on their pendants show more rust corrosion that thosewith Me. The Me would be hydrophobic, and this supports the idea thatthe pendant molecules are orientated away from the surface (as suggestedhereinabove). It is reasonable to assume these caps are available toengage in further organic reactions without effecting the basic surface.

SF19 showed the lowest corrosion performance of these materials butbecause of its average adhesion performance it was chosen for furtherexploratory tests as follows.

Tests with SF19 and Permabond 246 (described as a "Toughened Acrylic"adhesive) showed an increase in bond strength of 25% average over aseries of joints.

Tests with SF19 only on Loctite Anaerobic material (known only as "648")showed a 35% average increase in strength over a series of joints.

I claim:
 1. An abrading tool which comprises:a substrate on the surfaceof which, and optionally in the body of which, is carried an abrasivecomposition comprising an abrasive admixed with a rubbery siloxanecomposition which is the reaction product of a reactive polyfunctionalsiloxane co-polymerized with itself or with one or more other reactivepolyfunctional siloxane to form a rubbery-solid material, this reactionproduct being admixed with a liquid siloxane which is stably dispersedtherewithin.
 2. A tool as claimed in claim 1, which is a grinding wheel,disc or belt.
 3. A tool as claimed in claim 1, which is anabrasive-coated paper or non-woven cloth.
 4. A tool as claimed in claim3, wherein the abrasive is a mixture of a fine abrasive and a less fineabrasive.
 5. A tool as claimed in claim 1, wherein the abrasive isalumina.
 6. A tool as claimed in claim 1, wherein the rubbery siloxanecomposition is soft.
 7. A tool as claimed in claim 1, wherein therubbery composition is the cross-linked reaction product of apolyfunctional siloxane with either itself, with the assistance of across-linking agent, or with at least one other, different,polyfunctional siloxane, wherein each polyfunctional siloxane componentcontains at least three functional groups which may be the same ordifferent, and the said reaction product has a loose three-dimensionalmatrix capable of holding the liquid silicone therewithin.
 8. A tool asclaimed in claim 7, wherein the polyfunctional siloxane is a siliconepolymers made up of many units derived from moieties of the formula##STR4## wherein each of R¹ and R² is a methyl group.
 9. A tool asclaimed in claim 7, wherein the reaction product is formed by thereaction of a polysiloxane having amino functionality and a polysiloxanehaving dicarboxylic-anhydride functionality.
 10. A tool as claimed inclaim 1, wherein the liquid siloxane is a diorganyl siloxane of theGeneral Formula

     --O--Si(R.sub.2)--!

wherein each R group, which may be the same or different, is hydrogen ora hydrocarbyl or poly(oxyhydrocarbyl) group.
 11. A tool as claimed inclaim 10, wherein the siloxane is a friction-enhancer, and is a dimethylor a hydrogenmethyl siloxane.
 12. A tool as claimed in claim 10, whereinthe siloxane is suitable for use in excoriating/conditioning, and is apoly(oxyethylene)siloxane.
 13. A method of shaping an object in whichthe surface of the object is abraded away using a coarsely-abrasive toolas defined in claim
 1. 14. A method of conditioning a metal part byproviding it with a surface having bonded thereto a siloxane layer,which method includes the stages of first excoriating the part's surfaceunder oxygen-excluding conditions and, optionally in the presence of asiloxane, to clean off any oxide film therefrom and to leave the metalsurface bare and oxide-free, and then further rubbing the bare metalsurface in the presence of a siloxane in a substantially non-abrasivemanner to form on the clean surface said siloxane layer comprisingsiloxane molecules individually bonded directly to the surface.
 15. Aconditioning method as claimed in claim 14, in which the excoriationstage is effected using an abrading tool which comprises:a substrate onthe surface of which, and optionally in the body of which, is carried anabrasive composition comprising an abrasive admixed with a rubberysiloxane composition which is the reaction product of a reactivepolyfunctional siloxane co-polymerized with itself or with one or moreother reactive polyfunctional siloxanes to form a rubbery-solidmaterial, this reaction product being admixed with a liquid siloxanewhich is stably dispersed therewithin.
 16. A conditioning method asclaimed in claim 14, in which, to protect the bare metal surfaceproduced from ambient oxygen, the excoriation is effected using arubbing, abrasive tool that completely covers a relatively large area ata time, and is moved to rub in circles or zigzags that are small inrelation to the tool's surface area and that gradually translocateacross the metal surface.
 17. A conditioning method as claimed in claim14, wherein the further rubbing of the thus-cleaned surface is a simplecontinuation of the first stage.
 18. A metal part with a conditionedsurface, the surface having siloxane molecules each individually bondeddirectly to the metal over a relatively large area of the surface toprovide a relatively uniform siloxane layer.
 19. A conditioning methodas claimed in claim 14 in which the excoriation is effected with a toolusing abrasive-loaded nylon filaments, a non-woven abrasive material, acoated abrasive belt, a flap wheel or a cloth buff.
 20. A conditioningmethod as claimed in claim 14 in which the excoriation is effected witha tool using abrasive-loaded nylon filaments.